Thin films that are transparent in the visible light range and electrically conductive are used for transparent electrodes of new display systems such as liquid crystal displays, electroluminescence displays, and touch panels, and for prevention of static charge, blockage of electromagnetic waves or the like in transparent products.
Well-known examples of such transparent conductive thin films include conductive glass materials in which an indium oxide thin film is formed on a glass. However, such materials have a glass substrate and thus have poor flexibility or workability and cannot be used in some applications.
In recent years, therefore, transparent conductive thin films formed on a substrate of various plastic films such as polyethylene terephthalate films have been used, because of advantages such as good impact resistance and lightweight as well as flexibility and workability.
The transparent conductive thin film formed on such a film substrate has a relatively high surface optical reflectance and thus has the problem of low transparency. The conductive thin film formed on such a film substrate also has low abrasion resistance or low bending resistance and thus has a problem in which it can be scratched during use to increase the electric resistance or to cause disconnection.
Particularly when used in a touch panel, a pair of conductive thin films is opposed through a spacer and can be strongly brought into contact with each other by pressing and dotting from one panel plate side. Thus, it is strongly desired that the conductive thin films have good durability to withstand that and thus have good dotting properties, particularly pen input durability. However, the conventional transparent conductive thin films as described above are inferior in such durability and have a problem in which it makes the life of touch panels short, because of such low durability.
Therefore, some attempts have been made to overcome the above problems with the transparent conductive thin films formed on the film substrate. There is proposed a transparent conductive multilayer body in which a first transparent dielectric thin film, a second transparent dielectric thin film, and a transparent conductive thin film are laminated in this order on one side of a transparent film substrate with a thickness of 2 to 120 μm, while a transparent substrate is bonded to the other side of the film substrate through a transparent pressure-sensitive adhesive layer (see Japanese Patent Application Laid-Open (JP-A) No. 2002-316378 and JP-A No. 2002-326301).